Alkaline single cell gel electrophoresis of DNA fragments in biomonitoring for genotoxicity: an introductory study on healthy human volunteers.

Alkaline single cell gel electrophoresis (also known as the 'comet assay') is a rapid method for detecting DNA strand breaks in individual cells. Before the assay is used for biomonitoring in human populations the test conditions must be accurately characterised. Five healthy male volunteers donating capillary blood over a period of 20 weeks showed a fairly stable level of DNA damage in their lymphocytes. The values for tail moment and tail inertia, as evaluated by computerised image analysis of coded samples, were similar to those in lymphocytes from control mice but only 10% of those in lymphocytes from mice given cyclophosphamide (200 mg/kg b.wt.) 15-17 h before sacrifice. Inter- and intraindividual variations among the human subjects were related to both individual factors and laboratory conditions. When the comet assay is used for biomonitoring purposes it is suggested that each electrophoresis session should include not only the coded samples from the subjects, but also freshly isolated control cells and, in addition, cells that have been exposed to a well-characterised genotoxic insult.